Sorry bump! Interested to know this as my sis was saying something about it being brought in to our yard sometime in the near future and I know nothing about it
It was only a passing comment my sister made and unfortunately she didn't really have any details, she just said the YO is having a soya (based?) feed delivered sometime soon and she'd been asked if she wanted her horse to have any. YO told her it was good for putting condition or weight on. Sorry that's all she said before she had to head to work but it got me curious.
It just depends on the horse. If you notice IR symptoms and behavorial issues then talk to a professional or a nutritionist NOT associated with a big feed company. Trust me, they'll just think you're a fruitbat! Ask me how I know. My horses are thankful I take offense to be talked to like that and no longer have food issues.
In my opinion more people should be aware of soya intolerance in certain horses.